Wire-coating composition based on new polyester amide imides and polyester amides

ABSTRACT

Wire-coating composition containing resins with nucleophilic groups as well as possibly amide group-containing resins which are capable of crosslinking with one another, comprising (A) 5 to 95% by weight of at least one resin with nucleophilic groups selected from the group consisting of OH, NHR, SH, carboxylate and CH-acidic groups, (B) 0 to 70% by weight of at least one amide group-containing resin and (C) 5 to 95% by weight of at least one organic solvent, wherein the resins of either component (A) or component (B) contain α-carboxy-β-oxocycloalkyl carboxylic acid amide groups and the percent by weight of (A)-(C) adds up to 100 percent. The wire-coating compositions according to the invention allow a significant increase in the enamelling speed without losing the positive properties of standard wire enamels.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application 60/706,460, filed Aug. 8, 2005, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a new wire-coating composition based on new polyester amide imides and polyester amides which provides excellent enamelled surfaces of electrically conductive wires at elevated enamelling speeds, and is useful for coating of electric conductors.

BACKGROUND OF THE INVENTION

The wire-coating agents conventionally used nowadays are solutions of enamelled wire binders, such as, THEIC [tris(hydroxyethyl)isocyanurate] polyesters, polyesters, polyamides, polyamide-imides, THEIC polyester imides, polyester imides or polyurethanes in suitable organic solvents such as, cresol, phenol, benzyl alcohol, propylene carbonate or N-methylpyrrolidone, as well as diluents, such as, xylene, other substituted aromatic substances, aliphatic substances and small additions of additives, catalysts and regulators. The solvents are evaporated during thermal curing of the wire coating agents. In order to obtain a high-quality coating, it is necessary to drive out the solvents as completely as possible. In addition to the solvents, by-products of the curing reactions pass from the enamelling phase into the gas phase as occurs during crosslinking by condensation reactions.

After the wire coating has passed briefly through the enamelling installation, the user of the wire coating endeavours to increase the output of enamelled electrically conductive wire as much as possible and to obtain the best possible process for the user. Even at elevated enamelling speeds, not only the solvent but also cleavage products of the crosslinking reaction have to be removed as completely as possible from the enamel in order to achieve adequate crosslinking. The oven temperature or catalysis of the crosslinking reaction or both parameters therefore have to be increased to allow substantial crosslinking despite the relatively short residence time of the wire in the oven. The faster crosslinking leads to a rapid increase in viscosity, so the dissipation of solvent and condensation products also has to take place in a much shorter period of time. The process window therefore, becomes much smaller and the stability of the wire enamelling process is significantly restricted. The occurrence of specific enamel defects, such as, bubbles or craters is thus almost inevitable.

Various methods of increasing the speeds at which the wire enamels are applied to electrical conductors have been adopted in the past as shown in the following patents:

EP-A 873198 discusses an enamel which represents a polyamido amine bound to low-molecular acrylates by a Michael reaction.

DE-A 3133571 proposes a polyurethane wire enamelling system which contains tris(hydroxyethyl)isocyanurate in addition to a polyol and a (blocked) isocyanate component. This system allows a higher enamelling speed than a similar composition without tris(hydroxyethyl)isocyanurate. However, this method is restricted to polyurethane wire enamels.

DE-A 19648830 proposes a polyester imide wire enamelling resin which allows high enamelling speeds. A polyimide is initially produced by reacting polyisocyanate or polyamine with acid or acid anhydride, is reacted with a polyol to form a polyester imide and is subsequently reacted with acid or anhydride. This polyester imide is characterised, in particular, in that it also carries a significant number of acid groups in addition to hydroxy groups. The enamelling speed is limited by the OH—COOH esterification reaction, which generally takes place more slowly than a transesterification reaction.

SUMMARY OF THE INVENTION

The invention provides wire-coating composition containing resins with nucleophilic groups as well as possibly amide group-containing resins which are capable of crosslinking with one another, comprising

-   -   (A) 5 to 95% by weight of at least one resin with nucleophilic         groups selected from the group consisting of OH, NHR, SH,         carboxylate and CH-acidic groups,     -   (B) 0 to 70% by weight of at least one amide group-containing         resin and     -   (C) 5 to 95% by weight of at least one organic solvent, wherein         the resins of either component (A) or, if component B) is         contained in the composition, component (B) contain         α-carboxy-β-oxocycloalkyl carboxylic acid amide groups and the         percent by weight of (A)-(C) adds up to 100 percent.

The wire-coating composition according to the invention allows a significant increase in the enamelling speed without losing the positive properties of standard wire enamels. The wire-coating agents according to the invention are stable in storage and exhibit good adhesion to round and profiled electrically conductive wires and have adequate heat shock resistance. An extremely high surface quality is achieved with very good electrical, thermal and mechanical properties, in particular at high enamelling speeds. The enamels according to the invention surprisingly also have better adhesion and better mechanical properties than those of the prior art.

DETAILED DESCRIPTION

A wire-coating composition which additionally contains phenolic resins and/or melamine resins, catalysts, nano-scale particles and/or element-organic compounds, as well as, optionally conventionally used additives and/or auxiliaries and pigments and/or fillers is preferred.

Wire-coating compositions of this type comprise

-   -   (A) 5 to 60% by weight of at least one resin with nucleophilic         groups selected from the group consisting of OH, NHR, SH,         carboxylate and CH-acidic groups,     -   (B) 1 to 50% by weight of at least one amide group-containing         resin,     -   (C) 5 to 90% by weight of at least one organic solvent, (D) 0 to         10% by weight and preferably 0.1 to 10% by weight of at least         one catalyst,     -   (E) 0 to 20% by weight and preferably 0.1 to 20% by weight of at         least one phenolic resin and/or melamine resin and/or blocked         isocyanate,     -   (F) 0 to 3% by weight and preferably 0.1 to 3% by weight of         conventionally used additives or auxiliaries,     -   (G) 0 to 70% by weight and preferably 0.1 to 70% by weight of         nano-scale particles, and     -   (H) 0 to 60% by weight and preferably 0.1 to 60% by weight of         conventionally used fillers and/or pigments,     -   wherein the resins of either component (A) or component (B)         contain α-carboxy-β-oxocycloalkyl carboxylic acid amide groups         and the percent by weight of (A)-(H) adds up to 100 percent.

Resins which are known for the coating of wire may be used as component A). These may be polyesters, also, polyesters with heterocyclic nitrogen-containing rings, for example polyesters with imide and hydantoin and benzimidazole structures condensed into the molecule. The polyesters are, in particular, condensation products of polybasic aliphatic, aromatic and/or cycloaliphatic carboxylic acids and the anhydrides thereof, polyhydric alcohols and, in the case of the imide-containing polyesters, polyester amino group-containing compounds, optionally, with a proportion of monofunctional compounds, for example, monohydric alcohols. The saturated polyester imides are preferably based on terephthalic acid polyester which may also contain polyols and, as an additional dicarboxylic acid component, a reaction product of diaminodiphenylmethane and trimellitic acid anhydride in addition to diols. Furthermore, unsaturated polyester resins and/or polyester imides, as well as, polyacrylates may also be used. As component A the following may also be used: polyamides, for example, thermoplastic polyamides, aromatic, aliphatic and aromatic-aliphatic, also polyamide imides of the type produced, for example, from trimelletic acid anhydride and diisocyanato-diphenylmethane.

Unsaturated polyesters and/or polyester imides are preferably used.

The composition according to the invention can additionally contain one or more further binders of the type known and conventional in the wire coating industry. These may be, for example, polyesters, polyester imides, polyamides, polyamide imides, THEIC-polyester imides, polytitanic acid ester-THEIC-ester imides, phenolic resins, melamine resins, polymethacrylic imide, polyimides, polybismaleic imides, polyether imides, polybenzoxazine diones, polyhydantoins, polyvinylformals, polyacrylates and derivatives thereof, polyvinylacetals and/or masked isocyanates. Polyesters and THEIC-polyester imides are preferably used (Lit.: Behr, “Hochtemperaturbestandige Kunststoffe” Hanser Verlage, Munich 1969; Cassidy, “Thermally Stable Polymers” New York: Marcel Dekker, 1980; Frazer, “High Temperature Resistant Polymers” New York: Interscience, 1968; Mair, Kunststoffe 77 (1987) 204).

The amide-containing resins of component B) contain α-carboxy-β-oxocycloalkyl carboxylic acid amide groups as a component which is instrumental to the invention. The α-carboxy-β-oxocycloalkyl carboxylic acid amide groups are preferably incorporated in a terminal position. The aforementioned α-carboxy groups are preferably alkyl- or aryl-esterified. α-carboxy-β-oxocycloalkyl carboxylic acid amides of this type may be produced, on the one hand, from the corresponding carboxylic acid or the reactive derivatives thereof, such as, carboxylic acid halide groups, carboxylic acid anhydride groups or the like by reaction with amine groups. It is also expedient to use amidation auxiliaries, such as, dicyclohexylcarbodiimide during synthesis from amine and carboxylic acid. The α-carboxy-β-oxocycloalkyl carboxylic acids, in turn, may be obtained, for example, by reaction with haloformic acid esters under basic conditions and subsequent selective saponification. 1-carboxy-2-oxocycloalkanes may in turn be obtained synthetically, for example, from 1,n-carboxytic acid diesters by reaction with bases with alcohol cleavage. On the other hand, said α-carboxy-β-oxocycloalkyl carboxylic acid amides may also be produced by reaction of said 1-carboxy-2-oxocycloalkanes with isocyanates under basic condition. Said 1-carboxy-2-oxocycloalkanes may be obtained, for example, from glutaric acid dialkyl esters, glutaric acid diaryl esters, adipic acid dialkyl esters, adipic acid diaryl esters, pimelic acid dialkyl esters, pimelic acid diaryl esters, octanoic dyacid dialkyl esters, octanoic dyacid diaryl esters and the alkyl-, aryl-, alkoxy-, aryloxy-, alkylcarboxy-, arylcarboxy-, halogen- and otherwise substituted derivatives thereof, particularly preferably from adipic acid dimethyl and ethyl ester. The aforementioned isocyanates may be, for example, propylene diisocyanate, trimethylene diisocyanate, tetramethyle diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, ethylethylene diisocyanate, 3,3,4-trimethyl hexamethylene diisocyanate, 1,3-cyclopentyl diisocyanate, 1,4-cyclohexyl diisocyanate, 1,2-cyclohexyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,5-toluylene diisocyanate, 2,6-toluylene diisocyanate, 4,4′-biphenylene diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, polynuclear isocyanates which result from the reaction of aniline, formaldehyde and COCl₂ having functionality of >2,4,4′-dicyclohexylmethane diisocyanate, 2,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, triisocyanatononane or oligomers and polymers built up from these isocyanates (for example, uretdiones, isocyanurates or the like).

Excess urethanes or ureas obtained from said isocyanates, obtainable, for example, by reaction with ethylene glycol, propylene glycol, butane diol, 1,3-propane diol, hexane diol, neopentyl glycol, trimethylol propane, glycerine, pentaerythritol and other diols, triols, tetraols, polyols or else amino alcohols, diamines, triamines and polyamines may also be used.

The aforementioned amines used for amidation may be aliphatic primary diamines, such as, ethylene diamine, propylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, cycloaliphatic diamines such as, 4,4′-dicyclohexylmethane diamine or else triamines, and it is also possible to use secondary amines. The amines may also be aromatic amines, such as, diaminodiphenylmethane, phenylene diamine, polynuclear aromatic amines with a functionality of >2, toluylene diamines or corresponding derivatives. It is also possible to use amines with a further functional group in the molecule, for example, amino alcohols such as, monoethanol amine and/or monopropanol amines, or amino acids, such as, glycine, aminopropanoic acids, aminocaproic acids or aminobenzoic acids and the esters thereof.

The α-carboxy-β-oxocycloalkyl carboxylic acid amide groups may also be incorporated directly into component A). This can be achieved, for example, by reaction of the resin of component A) with di- or polyisocyanates and at least one carboxy-β-oxocycloalkane.

As the component C), the compositions can contain one or more organic solvents, such as, aromatic hydrocarbons, N-methylpyrrolidone, cresols, phenols, xylenols, styrenes, vinyl toluene, methylacrylates.

Catalysts, such as, tetrabutyl titanate, isopropyl titanate, cresol titanate, the polymeric forms thereof, dibutyl tin dilaurate, further tin catalysts, may be used, individually or in a mixture, as the component D).

Phenolic resins and/or melamine resins which may be used as the component E) may be, for example, novolaks, obtainable by polycondensation of phenols and aldehydes or polyvinyl formals, obtainable from polyvinyl alcohols and aldehydes and/or ketones.

Blocked isocyanates, such as, NCO-adducts of polyols, amines, C—H-acidic compounds (for example, acetoacetic esters, malonic esters, etc.) and diisocyanates (for example, Lit. Methoden der org. Chemie, Houben-Weyl, Georg Thieme Verlag, Stuttgart, 4th edition, Vol. 14/2, Part 2 “Makromolekulare Stoffe”, 1963, page 61) may also be used as the component E, cresols and/or phenols conventionally being used as blocking agents.

Conventional additives and auxiliaries of component F) include, for example, conventional enamel additives, such as, extenders, plasticising components, accelerators (for example metal salts, substituted amines), initiators (for example photo initiators, heat-responsive initiators), stabilisers (for example, hydroquinones, quinones, alkylphenols, alkylphenol ethers), defoamers and flow control agents.

Nano-scale particles of component G) include particles with an average particle size in the range of 1 to 300 nm, preferably in the range of 2 to 80 nm. These are, for example, inorganic nano-scale particles based on compounds, such as, Si0₂, Al₂O₃, TiO₂, boronitride, silicon carbide. The particles can be, for example, compounds based on an element-oxygen network comprising elements from the series consisting of silicon, zinc, aluminium, tin, boron, germanium, gallium, lead, the transition metals and the lanthanides and actinides, in particular, from the series consisting of silicon, titanium, zinc, yttrium, cerium, vanadium, hafnium, zirconium, nickel and/or tantalum. The surface of the element-oxygen network of these particles being modifiable with reactive organic groups, as described, for example, in EP-A 1166283.

The compositions may contain as the component H) pigments and/or fillers, for example based on SiO₂, Al₂O₃, TiO₂, Cr₂O₃, for example, colour-imparting inorganic and/or organic pigments, such as, titanium dioxide or carbon black and effect pigments, such as, metal flake pigments and/or pearlescent pigments.

The coating composition can additionally contain monomeric and/or polymeric element-organic compounds. Examples of polymeric organo-element compounds include inorganic-organic hybrid polymers of the type mentioned, for example, in DE-A 198 41 977. Examples of monomeric organo-element compounds include ortho-titanic acid esters and/or ortho-zirconic acid esters such as, nonyl, cetyl, stearyl, triethanolamine, diethanolamine, acetylacetone, acetoacetic ester, tetraisopropyl, cresyl, tetrabutyltitanate and zirconate as well as titanium tetralactate, hafnium and silicon compounds, for example hafnium tetrabutoxide and tetraethyl silicate and/or various silicone resins. Additional polymeric and/or monomeric organo-element compounds of this type may be contained, for example in a content of 0 to 70% by weight, in the composition according to the invention.

Component A) and component B) can enter chemical reactions during the stoving (baking) process. Depending on the chemical nature of components A) and B), suitable reactions known to the person skilled in the art include, for example, an ester interchange reaction, polymefisation reaction, polyaddition reaction, condensation reaction. Addition reactiorvs between component A) and B), for example, ring opening in B) by nucleophilic attack of A), are preferred. A polyester amide imide wire coating or a polyester amide wire coating is formed by the chemical reactions during the stoving process.

The composition according to the invention may optionally also be mixed with conventional wire enamels and subsequently be applied by conventional methods.

The composition according to the invention may be applied by conventional methods independently of the type and diameter of the electrically conductive wire used. The wire may be coated directly with the composition according to the invention and subsequently be stoved (baked) in an oven. Coating and stoving may optionally take place several times in succession. The ovens may be arranged horizontally or vertically, the coating conditions, such as, duration and number of coatings, stoving temperature, coating speed being adapted to the type of wire to be coated. For example, the coating temperatures may lie in a range from room temperature to 400° C. In addition, ambient temperatures above 400° C., for example of up to 800° C. and higher, may be possible during the enamelling process without affecting the quality of the coating according to the invention. The stoving may be supported by irradiation with infrared (IR) and/or near infrared (NIR) radiation with techniques known for a person skilled in the art.

The composition according to the invention may be used independently of the type and diameter of the electrically conductive wire; for example, wires having a diameter of 5 μm to 6 mm may be coated. The conventional metallic conductors made, for example, of copper, aluminium, zinc, iron, gold, silver or alloys thereof may be used as the wires.

The coating composition according to the invention may be contained as a component of a multilayer enamel. This multilayer enamel can contain, for example, at least one coating composition according to the invention.

According to the invention, the electrically conductive wires may be coated with or without existing finishes. Existing finishes may be, for example, insulating coatings and flame-retardant coatings. In such cases, the layer thickness of the coating according to the invention can differ greatly.

It is also possible to apply further coatings, for example, further insulating coatings, via the coating according to the invention. These coatings may also be used, for example, as a topcoat, to improve mechanical protection and create desired surface properties as well as providing a smooth surface. For example, compositions based on polyamides, polyamides imides and polyimides are particularly suitable as topcoats.

In particular, the composition according to the invention is also suitable as a single-layer application.

According to the invention, the composition may be applied in conventional layer thicknesses. Thin layers of, for example, 5 to 10 μm may also be applied without influencing the resistance to partial discharge achieved according to the invention nor the adhesion, strength and extensibility of the finishes. The dry layer thickness can vary, according to the standardised values for thin and thick electrically conductive wires, for example, for thin wires in low thicknesses of 5 to 10 μm, and for thick wires in thicknesses of about 75 to 89 μm.

The invention will be described with reference to the following examples:

EXAMPLES

Tests:

Solids content 1 g, 1 h, 180° C. [%] corresponding to DIN EN ISQ 3251

Viscosity at 25° C. [mpas] or [Pas] corresponding to DIN 53015

Example 1 THEIC-Polyesterimide as the Component A

122.4 g ethylene glycol, 37.5 g propylene glycol, 171.5 g dimethylterephthalate (DMT), 237.7 g tris(hydroxyethyl)isocyanurate (THEIC) and 1.0 g ortho-titanic acid-tetra-butyl ester are heated to 205° C. in 4 hours in a 2-litre three-neck flask with stirrer, thermometer and distillation unit (column and distillation bridge). 55 g methanol are distilled off. After cooling to 150° C., 277.8 g trimellitic acid anhydride (TMA) and 143.2 g methylenedianiline (DADM) are added. The mixture is heated to 210° C. within 3 hours while stirring and is kept at this temperature until the solid resin has reached a viscosity of 710 mPas (1:2 in m-cresol, 25° C.). 52 g water are distilled off. The residue is now cooled to 180° C. and 509 g cresol are added. The resultant polyester imide solution has a solids content of 60.3%.

Example 2 THEIC-Polyester as the Component A

105.9 g ethylene glycol, 464.5 g dimethylterephthalate (DMT), 416.6 g tris(hydroxyethyl)isocyanurate (THEIC), 0.4 g zinc acetate and 0.4 g ortho-titanic acid-tetra-butyl ester are heated to 220° C. within 3 hours while stirring in a 2-litre three-neck flask with stirrer, thermometer and distillation unit (column and distillation bridge) and kept at this temperature until the solid resin has reached a viscosity of 700 mPas (1:2 in m-cresol, 25° C.). 153 g water are distilled off. The mixture is now cooled to 180° C. and 490.5 g cresol are added along with 21.6 g ortho-titanic acid-tetra-butyl ester at 150° C. max. The resultant polyester solution has a solids content of 59.7%.

Example 3 Amide Group-Containing Polyurethane Resin as the Component B

150.0 g xylene, 346.5 g Desmodur® 44 M, Please identify 0.2 g of a conventional catalyst (for example, hydroxide), 49.6 g trimethylol propane and 216.5 g 2-oxo-cyclopentyl carboxylic acid ethyl ester are heated to 70° C. in a 2-litre three-neck flask with stirrer, reflux condenser and thermometer, until the NCO-number has fallen to <6.5% after approx. 4 hours. The mixture is then cooled to 40° C., 160.0 g of a polyester imide resin solution (solids content 30.2% in cresol, hydroxyl number 322 mgKOH/g) are added and heated to 140° C. A viscosity of 1040 mPas (4:4 in cresol, 25° C.) is achieved after 3 hours. The mixture is then diluted with 577.2 g cresol and the resin filtered. The resultant amidourethane resin solution has a viscosity of 5500 mPas at 25° C. and a solids content of 44.6%.

Example 4 Amide Group-Containing Polyester Resin as the Component B

150.0 g xylene, 272.2 g Desmodur®44 M (described in Example 3), 0.2 g of a conventional catalyst (for example, hydroxide) and 340.0 g 2-oxo-cyclopentyl carboxylic acid ethyl ester are heated to 70° C. in a 2-litre three-neck flask with stirrer, reflux condenser and thermometer, until the NCO-number has dropped to <0.5% after approx. 4 hours. The mixture is then cooled to 40° C., 48.7 g trimethylol propane are added and heated to 140° C. A viscosity of 1150 mPas (4:5 in cresol, 25° C.) is achieved after 3 hours. The mixture is then diluted with 688.9 g cresol and the resin filtered. The resultant amido ester resin solution has a viscosity of 4800 mPas at 25° C. and a solids content of 44.5%.

Example 5 Amido Group-Containing Resin as the Component B

150.0 g xylene, 304.0 g Desmodur® VL (please identify), 0.2 g of a conventional catalyst (for example hydroxide) and 356.9 g 2-oxo-cyclopentylcarboxylic acid ethyl ester are heated to 70° C. in a 2-litre three-neck flask with stirrer, reflux condenser and thermometer until the NCO number has dropped to <0.5% after approx. 4 hours. A viscosity of 980 mPas (4: 5 in cresol, 25° C.) is reached after 3 hours. The mixture is then diluted with 688.9 g cresol and the resin filtered. The resultant amide resin solution has a viscosity of 4200 mPas at 25° C. and a solids content of 44.6%.

Example 6 Polyester Imide Enamel Compared to Polyester Amide Imide Enamel According to the Invention

Enamel 6a (prior art):

653.1 g of the polyester imide solution from Example 1, 211.2 g cresol, 86.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.7% and a viscosity at 25° C. of 1250 mPas.

Enamel 6b:

479.0 g of the polyester imide solution from Example 1, 214.0 g of the amido urethane resin solution for Example 3, 173.3 g cresol, 84.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.9% and a viscosity at 25° C. of 1320 mPas.

Enamel 6c:

384.0 g of the polyester imide solution from Example 1, 342.0 g of the amido urethane resin solution for Example 3, 142.3 g cresol, 82.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.2% and a viscosity at 25° C. of 1400 mpas.

Enamel 6d:

274.0 g of the polyester imide solution from Example 1, 490.0 g of the amido urethane resin solution for Example 3, 106.3 g cresol, 80.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 40.0% and a viscosity at 25° C. of 1420 mpas.

Enamel 6e:

175.0 g of the polyester imide solution from Example 1, 625.0 g of the amido urethane resin solution for Example 3, 72.3 g cresol, 78.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.4% and a viscosity at 25° C. of 1500 mpas.

Example 7 (Polyester Enamel Compared to Polyester Amide Enamel According to the Invention

Enamel 7a (prior art):

745.0 g of the polyester solution from Example 2, 15.0 g cresol, 29.0 g benzyl alcohol, 42.0 g cyclohexanone, 52.0 g methyidiglycol, 10.0 g aromatic hydrocarbon mixture A, 30.0 g aromatic hydrocarbon mixture B and 68.0 g of conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 50.4% and a viscosity at 25° C. of 3920 mPas.

Enamel 7b:

591.0 g of the polyester solution from Example 2, 207.0 g of the amido urethane resin solution from Example 3, 11.0 g cresol, 21.0 g benzyl alcohol, 30.0 g cyclohexanone, 38.0 g methyidiglycol, 7.0 g aromatic hydrocarbon mixture A, 27.0 g aromatic hydrocarbon mixture B and 68.0 g of conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 50.0% and a viscosity at 25° C. of 4050 mpas.

Enamel 7c:

490.0 g of the polyester solution from Example 2, 342.0 g of the amido urethane resin solution from Example 3, 9.5 g cresol, 16.0 g benzyl alcohol, 22.5 g cyclohexanone, 27.0 g methyldiglycol, 5.0 g-aromatic hydrocarbon mixture A, 20.0 g aromatic hydrocarbon mixture B and 68.0 g of conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 49.6% and a viscosity at 25° C. of 4240 mPas.

Enamel 7d:

366.0 g of the polyester solution from Example 2, 508.0 g of the amido urethane resin solution from Example 3, 6.5 g cresol, 9.5 g benzyl alcohol, 13.0 g cyclohexanone, 15.0 methyldiglycol, 3.0 g aromatic hydrocarbon mixture A, 11.0 g aromatic hydrocarbon mixture B and 68.0 g of conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 49.9% and a viscosity at 25° C. of 4430 mpas.

Enamel 7e:

243.0 g of the polyester solution from Example 2, 673.0 g of the amido urethane resin solution from Example 3, 1.0 g cresol, 2.0 g benzyl alcohol, 4.0 g cyclohexanone, 5.0 methyidiglycol, 1.0 g aromatic hydrocarbon mixture A, 3.0 g aromatic hydrocarbon mixture B and 68.0 g of conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 49.4% and a viscosity at 25° C. of 4510 mPas.

Example 8 Polyester Imide Enamel Compared to Polyester Amide Imide Enamel According to the Invention

Enamel 8a (prior art):

653.1 g of the polyester imide solution from Example 1, 211.2 g cresol, 86.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring.

The resultant wire enamel has a solids content of 39.7% and a viscosity at 25° C. of 1250 mPas (corresponding to enamel 6a).

Enamel 8b:

448.8 g of the polyester imide solution from Example 1, 254.8 g of the amido ester resin solution from Example 4, 166.7 g cresol, 81.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring.

The resultant wire enamel has a solids content of 39.5% and a viscosity at 25° C. of 1200 mpas.

Enamel 8c:

346.5 g of the polyester imide solution from Example 1, 393.4 g of the amido ester resin solution from Example 4, 138.2 g cresol, 78.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring.

The resultant wire enamel has a solids content of 39.9% and a viscosity at 25° C. of 1250 mpas.

Enamel 8d:

238.0 g of the polyester imide solution from Example 1, 540.0 g of the amido ester resin solution from Example 4, 95.9 g cresol, 76.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring..

The resultant wire enamel has a solids content of 39.8% and a viscosity at 25° C. of 1310 mPas.

Enamel 8e:

146.3 g of the polyester imide solution from Example 1, 664.6 g of the amido ester resin solution from Example 4, 65.4 g cresol, 74.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of conventional commercial surface additives and phenolic resins are made up into an enamel while stirring.

The resultant wire enamel has a solids content of 39.2% and a viscosity at 25° C. of 1290 mPas.

Example 9 Polyester Enamel Compared to Polyester Amide Enamel According to the Invention

Enamel 9a (prior art):

745.0 g of the polyester solution from Example 2, 15.0 g cresol, 29.0 g benzyl alcohol, 42.0 g cyclohexanone, 52.0 g methyidiglycol, 10.0 g aromatic hydrocarbon mixture A, 39.0 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 50.4% and a viscosity at 25° C. of 3920 mPas (corresponding to enamel 7a).

Enamel 9b:

559.8 g of the polyester solution from Example 2, 249.0 g of the amido ester resin solution from Example 4, 10.0 g cresol, 19.0 g benzyl alcohol, 28.0 g cyclohexanone, 35.0 g methyldiglycol, 6.0 g aromatic hydrocarbon mixture A, 25.2 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 49.8% and a viscosity at 25° C. of 3870 mpas.

Enamel 9c:

448.2 g of the polyester solution from Example 2, 398.8 g of the amido ester resin solution from Example 4, 8.0 g cresol, 14.0 g benzyl alcohol, 18.5 g cyclohexanone, 23.5 g methyldiglycol, 4.0 g aromatic hydrocarbon mixture A, 17.0 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 49.9% and a viscosity at 25° C. of 4010 mpas.

Enamel 9d:

320.4 g of the polyester solution from Example 2, 570.2 g of the amido ester resin solution from Example 4, 4.4 g cresol, 7.0 g benzyl alcohol, 9.0 g cyclohexanone, 11.0 g methyidiglycol, 2.0 g aromatic hydrocarbon mixture A, 8.0 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 50.2% and a viscosity at 25° C. of 4230 mpas.

Enamel 9e:

204.0 g of the polyester solution from Example 2, 726.3 g of the amido ester resin solution from Example 4, 1.7 g benzyl alcohol and 68.0 g conventional commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 50.6% and a viscosity at 25° C. of 4300 mpas.

Example 10 Polyester Imide Enamel Compared to Polyester Amide Imide Enamel According to the Invention

Enamel 10a (prior art):

653.1 g of the polyester imide solution from Example 1, 211.2 g cresol, 86.0 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.7% and a viscosity at 25° C. of 1259 mPas (corresponding to enamel 6a).

Enamel 10b:

530.7 g of the polyester imide solution from Example 1, 143.5 g of the amide resin solution from Example 5, 185.5 g cresol, 90.6 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.6% and a viscosity at 25° C. of 1150 mpas.

Enamel 10c:

454.9 g of the polyester imide solution from Example 1, 246.0 g of the amide resin solution from Example 5, 158.5 g cresol, 90.9 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.5% and a viscosity at 25° C. of 1170 mPas.

Enamel 10d:

353.8 g of the polyester imide solution from Example 1, 382.7 g of the amide resin solution from Example 5, 124.6 g cresol, 89.2 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 39.8% and- a viscosity at 25° C. of 1210 mPas.

Enamel 10e:

244.9 g of the polyester imide solution from Example 1, 529.9 g of the amide resin solution from Example 3, 95.3 g cresol, 80.2 g aromatic hydrocarbon mixture, 30.6 g benzyl alcohol, 10.2 g of a conventional commercial catalyst A and small amounts (8.9 g) of commercial surface additives and phenolic resins are made up into an enamel while stirring. The resultant wire enamel has a solids content of 40.1 % and a viscosity at 25° C. of 1240 mPas.

Example 11 Polyester Enamel Compared with Polyester Amide Enamel According to the Invention

Enamel 11 a (prior art):

745.0 g of the polyester solution from Example 2, 15.0 g cresol, 29.0 g benzyl alcohol, 42.0 g cyclohexanone, 52.0 g methyldiglycol, 10.0 g aromatic hydrocarbon mixture A, 39.0 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 50.4% and a viscosity at 25° C. of 3920 mPas (corresponding to enamel 7a).

Enamel 11 b:

643.5 g of the polyester solution from Example 2,136.4 g of the amide resin solution from Example 5, 12.5 g cresol, 24.0 g benzyl alcohol, 34.5 g cyclohexanone, 44.0 g methyldiglycol, 8.0 g aromatic hydrocarbon mixture A, 29.1 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 49.8% and a viscosity at 25° C. of 3850 mpas.

Enamel 11c:

566.1 g of the polyester solution from Example 2, 240.0 g of the amide resin solution from Example 5, 11.3 g cresol, 19.6 g benzyl alcohol, 27.9 g cyclohexanone, 34.2 g methyidiglycol, 6.9 g aromatic hydrocarbon mixture A, 26.0 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 49.6% and a viscosity at 25° C. of 3040 mpas.

Enamel 11d:

456.4 g of the polyester solution from Example 2, 386.9 g of the amide resin solution from Example 5, 8.7 g cresol, 13.9 g benzyl alcohol, 19.6 g cyclohexanone, 23.8 g methyldiglycol, 5.2 g aromatic hydrocarbon mixture A, 17.5 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 49.7% and a viscosity at 25° C. of 4030 mpas.

Enamel 11e:

328.8 g of the polyester solution from Example 2, 557.6 g of the amide resin solution from Example 5, 3.2 g cresol, 6.3 g benzyl alcohol, 10.3 g cyclohexanone, 13.4 g methyidiglycol, 3.2 g aromatic hydrocarbon mixture A, 9.2 g aromatic hydrocarbon mixture B and 68.0 g conventional commercial surface additives and phenolic resins are made up to an enamel while stirring. The resultant wire enamel has a solids content of 49.5% and a viscosity at 25° C. of 4100 mpas.

Results

Test data according to DIN 46453 and DIN EN 60851:

Polyester Imides (Examples 6. 8 and 10)

0.65 mm diameter copper wire was enamelled at an oven temperature of 580° C., at 38 and 46 m/min respectively.

With amido urethane resin: Enamel 6a 6b 6c 6d 6e 6a 6b 6c 6d 6e Enamelling 38 38 38 38 38 48 48 48 48 48 speed (m/min) Increase in 65 65 66 65 67 66 65 64 66 66 enamel (μm) Enamel OK OK OK OK OK Not Not OK OK OK surface OK OK Softening OK OK OK OK OK Not Not Almost OK OK temperature OK OK OK (380° C.) Tangent 195 197 197 196 190 172 183 193 194 189 delta Steep rise (° C.) Coil 20 20 20 25 25 10 15 20 25 25 resistance [%] (Mandrel test) Heat shock 220 210 220 220 200 180 200 210 220 220 [° C.] (1 × d) Breakdown 8440 8270 8620 8420 8040 4600 5420 6940 7930 8140 voltage (volts)

With amido ester resin: Enamel 8a 8b 8c 8d 8e 8a 8b 8c 8d 8e Enamelling 38 38 38 38 38 48 48 48 48 48 speed (m/min) Increase in 65 63 67 64 66 66 66 64 65 67 enamel (μm) Enamel OK OK OK OK OK Not OK OK OK OK surface OK Softening OK OK OK OK OK Not Not OK OK OK temperature OK OK (380° C.) Tangent 195 198 200 200 199 172 187 197 196 195 delta Steep rise (° C.) Mandrel 20 20 25 25 25 10 15 20 25 25 Test Heat shock 220 220 220 220 220 180 200 220 220 220 Breakdown 8440 8210 8300 8640 8710 4600 5700 7150 8450 7900 voltage (volts)

With amide resin: Enamel 10a 10b 10c 10d 10e 10a 10b 10c 10d 10e Enamelling 38 38 38 38 38 48 48 48 48 48 speed (in/min) Increase in 65 67 66 67 67 65 65 67 66 67 enamel (μm) Enamel OK OK OK OK OK Not OK OK OK OK surface OK Softening OK OK OK OK OK Not Not OK OK OK temperature OK OK (380° C.) Tangent 195 198 199 205 205 172 189 200 204 201 delta Steep rise (° C.) Mandrel 20 20 20 20 20 10 15 20 20 25 Test Heat shock 220 220 220 220 220 180 200 220 220 220 Breakdown 8440 7990 8110 8530 8530 4600 6100 7700 8540 8200 voltage (volts)

The tables show clearly that, the higher the content of amide group-containing resin, the better the enamels maintain their general properties when the enamelling speed is changed markedly from 38 to 48 m/min (i.e. the enamels according to the invention exhibit better performance with rapid enamelling). The comparison enamel (a), on the contrary, exhibits significant losses of performance when the enamelling speed is increased.

Polyesters (Examples 7, 9 and 11):

1.0 mm diameter copper wire was enamelled at an oven temperature of 560° C. at 45 and 52 m/min respectively.

With amido urethane resin: Enamel 7a 7b 7c 7d 7e 7a 7b 7c 7d 7e Enamelling 45 45 45 45 45 52 52 52 52 52 speed (m/min) Increase in 82 84 82 81 83 84 82 81 83 82 enamel (μm) Enamel OK OK OK OK OK Not Not OK OK OK surface OK OK Softening OK OK OK OK OK Not Not OK OK OK temperature OK OK (400° C.) Tangent 176 178 176 175 177 142 155 169 174 172 delta Steep rise (° C.) Mandrel 20 20 20 20 20 10 15 20 20 20 test Heat shock 170 170 170 170 170 130 150 160 170 170 Breakdown 7700 7340 7420 7690 7580 4670 4950 5210 6630 7210 voltage (volts)

With amido ester resin: Enamel 9a 9b 9c 9d 9e 9a 9b 9c 9d 9e Enamelling 45 45 45 45 45 52 52 52 52 52 speed (m/min) Increase in 82 85 83 81 84 84 83 84 83 84 enamel (μm) Enamel OK OK OK OK OK Not Not OK OK OK surface OK OK Softening OK OK OK OK OK Not Not OK OK OK temperature OK OK (400° C.) Tangent 176 178 180 185 190 142 162 175 180 184 delta Steep rise (° C.) Mandrel 20 20 20 20 20 10 15 20 20 20 test Heat shock 170 170 180 190 200 130 150 170 180 190 Breakdown 7700 7400 7500 7550 7600 4670 4800 7550 7860 7330 voltage (volts)

With amide resin: Enamel 11a 11b 11c 11d 11e 11a 11b 11c 11d 11e Enamelling 45 45 45 45 45 52 52 52 52 52 speed (m/min) Increase in 82 85 83 82 86 84 83 85 84 84 enamel (μm) Enamel OK OK OK OK OK Not Not OK OK OK surface OK OK Softening OK OK OK OK OK Not Not OK OK OK temperature OK OK (400° C.) Tangent 176 182 187 196 201 142 164 182 185 190 delta Steep rise (° C.) Mandrel 20 20 20 20 20 10 15 20 20 20 Test Heat shock 170 180 180 190 200 130 150 160 180 180 Breakdown 7700 7530 7760 7580 7710 4670 5150 5900 7140 7800 voltage (volts)

The tables show clearly that, the higher the content of amide group-containing resin, the better the enamels maintain their general properties when the enamelling speed is changed markedly from 45 to 52 m/min (i.e. the enamels according to the invention exhibit better performance with rapid enamelling). The comparison enamel (a), on the contrary, exhibits significant losses of performance when the enamelling speed is increased. In addition, enamels 9 and 11 exhibit a significant improvement in heat shock in comparison with the standard (9a, 11a). 

1. A wire-coating composition based on resins with nucleophilic groups comprising (A) 5 to 95% by weight of at least one resin with nucleophilic groups selected from the group consisting of OH, NHR, SH, carboxylate and CH-acidic groups, (B) 0 to 70% by weight of at least one amide group-containing. resin and (C) 5 to 95% by weight of at least one organic solvent, wherein the resins of either component (A) or component (B) contain α-carboxy-β-oxocycloalky carboxylic acid amide groups, and the percent of by weight of (A)-(C) adds up to 100 percent.
 2. The composition according to claim 1 comprising (A) 5 to 60% by weight of at least one resin with nucleophilic groups selected from the group consisting of OH, NHR, SH, carboxylate and CH-acidic groups, (B) 1 to 50% by weight of at least one amide group-containing resin, (C) 5 to 90% by weight of at least one organic solvent, (D) 0 to 10% by weight of at least one catalyst, (E) 0 to 20% by weight of at least one phenolic resin and/or melamine resin and/or blocked isocyanate, (F) 0 to 3% by weight of conventionally used additives or auxiliaries, (G) 0 to 70% by weight of nano-scale particles, and (H) 0 to 60% by weight of conventionally used fillers and/or pigments, wherein the resins of either component (A) or component (B) contain the α-carboxy-β-oxocycloalkyl carboxylic acid amide groups, and the percent by weight of (A)-(H) adds up to 100 percent.
 3. The composition according to claim 2 wherein component B) contains α-carboxy-β-oxocycloalkyl carboxylic acid amide groups.
 4. The composition according to claim 1 wherein at least one polyester and /or polyester imide is used as component A).
 5. The composition according to claim 2 wherein the particles of component G) have an average particle size in the range of 1 to 300 nm.
 6. The composition according to claim 5 wherein the particles based on an element-oxygen network comprising elements from the series consisting of silicon, zinc, aluminium, tin, boron, germanium, gallium, lead, the transition metals and the lanthanides and actinides, and the surface of the element-oxygen network of these particles being modifiable with reactive organic groups.
 7. The composition according to claim 1 comprising element-organic compounds.
 8. The composition according to claim 7 wherein ortho-titanic acid esters, ortho-zirconic acid esters, titanium tetralactate, hafnium and silicon compounds and silicone resins are used as element-organic compounds.
 9. A process of coating electrically conductive wires comprising the steps of applying the composition according to claim 1 and curing said coating composition at an elevated temperature to produce a cured coating.
 10. The process according to claim 9 wherein the wire is pre-coated.
 11. The process according to claim 9 wherein the coating composition is applied as a single-layer and/or as a base coat, middle coat and/or top coat within a multi-layer coating.
 12. Electrically conductive wire coated with the coating composition according to claim 1 and cured. 